Longfin eel Anguilla dieffenbachii

Description

• Eels are very long fish characterised by having their dorsal and anal fins merged with the tail, and two small paired fins by their head.
• They are dark brown to grey-black in colour and their tiny scales are embedded in their skin, giving them a smooth feel.
• Longfin eels can be distinguished from shortfin eels by the dorsal fin being much longer than the anal fin so that it comes further forward towards the head. Longfin eels also form big skin wrinkles when they bend.

Interesting Facts

• Longfin eels are unique to New Zealand and have great cultural significance.
• They are widespread, including long distances inland (almost as far from the sea as possible).
• Eels eat a diverse range of foods including insects, small fish, and even mice and small birds.
• Eels can take 30 or more years to reach sexual maturity and lay their eggs way out in the Pacific Ocean.
• The wee larvae can take up to two years to return to New Zealand waters, during the spring whitebait season.
• River species require good riparian cover, streamside shade and logs and/or boulders instream.

Association with Plantations

• All indigenous fish species can occur in, or move through, plantation forestry areas.
• Plantation streams and lakes often have relatively high populations.

Threats

• Destruction of riparian vegetation.
• Competition and predation from introduced fish species.
• Commercial fishing.
• Habitat destruction from:
  • Modification of riparian margins.
  • Introduction of aquatic weeds.
  • Siltation.
  • Eutrophication (high nutrients).
  • Erosion of banks through grazing by livestock, goats and deer.

Management Options and Methods

• Maintain corridors of riparian vegetation along banks. Corridors should be as extensive as possible (refer to Buxton 1991).
• If possible, expand width of riparian zones during later rotation planting.
• Exclude livestock from riparian areas.
• Control deer and goats that could enter riparian areas.
• Comply with best forest operational management practices to avoid damage to riparian areas.
• Provide adequate fish passage through any artificial barriers within streams, e.g. building up downstream side of culverts with Gabion baskets of boulders or using other designs (refer Buxton 1991, Jowett 1999).
• Manage or prevent water abstraction from critical habitat areas.
• Regulate or prevent fishing of threatened species.
• Prevent introductions of exotic fish.
• Prevent introductions of aquatic weeds. Educate local users of weed threats and how to prevent spread.

Monitoring Options

• Undertake surveys to identify fisheries values and species.
• Consider repeating fish surveys every few years to ascertain whether key species are still present.
• Liaise with DOC about fish survey and monitoring methods.
• Report findings to DOC.
• Periodic checks of banks to ensure compliance with best forest operational management practices, pest and weed levels and siltation.

Further Information and Support

• DOC – advice for management, survey, and monitoring. Website http://www.doc.govt.nz/
• Buxton 1991. New Zealand’s wetlands: a management guide. Wellington, Department of Conservation.
• Jowett I. et al. 1999. Fish passage at culverts: a review with possible solutions for New Zealand indigenous species.
• McDowall R.M. 2000. The Reed Guide to Freshwater Fishes.
• NIWA website, Atlas of New Zealand freshwater fishes. Contains detailed identification guides and location maps. http://www.niwa.cri.nz/rc/freshwater/fishatlas